Medical instruments and parenteral drugs are sterilized prior to use. A traditional sterilization process uses steam under pressure. Alternative sterilization processes use ethylene oxide, hydrogen peroxide, or peracetic acid in the vapor form as the sterilant.
Sterilization processes using peracid solutions may be performed in a sterilization chamber. During a typical sterilization cycle, the instruments being sterilized are exposed to a sterilization solution containing, for example about 2000 ppm or 2500 ppm of peracetic acid. The instruments are exposed to the solution for a sufficient time at a sufficiently high enough temperature, e.g., 50xc2x0 C.-60xc2x0 C., for the sterilization to be effective.
The invention features monitoring a sterilization process that uses a vapor including a peracid (e.g., peracetic acid) with a monitor composition. The monitor composition contains a colorant and a halogen source. During the sterilization process, the peracid contacts the monitor composition, resulting in halogenation of the colorant to occur. Halogenation of the colorant causes the colorant and the monitor composition to undergo a distinct, permanent color change that provides an indication that sterilization has occurred. A distinct color change in the indicator composition occurs if normal medical professionals can readily discern the color change through visual observation.
Preferred colorants include dyes such as the sodium salt of fluorescein or phenol red that is susceptible to halogenation.
The invention also features sterilization indicators including a substrate and the indicator composition, as well as the indicator composition itself. The indicator composition can be used, for example, on indicating labels, or indicator tapes, and in devices that monitor the variables of a sterilization process (e.g., time, temperature, and concentration).
In another aspect, the invention features a monitor composition for monitoring a sterilization process including peracid, e.g., peracetic acid. The monitoring composition contains a colorant and a halogen source. When the monitoring composition is exposed to the peracid during a sterilization process the peracid causes halogenation of the colorant, which causes the monitoring composition to undergo a color change. The halogenated colorant may in turn be susceptible to additional reactions which cause the monitoring composition to undergo a further distinct color change, dependent upon, e.g., the concentration of the peracid in the solution. The colorant may be a dye such as phenol red.
The invention also features a method of monitoring peracid liquid phase sterilization processes. The monitor composition includes a colorant and is exposed to a solution including peracid during a sterilization process. The monitoring composition will change to a particular color if the sterilization process meets certain pre-determined sterilization parameters, such as exposure time, exposure temperature, and exposure concentration of peracid (e.g., 1 minute, 25xc2x0 C., and 1000 ppm of peracid).
The invention also features a method of determining whether a solution including peracid has a concentration of peracetic acid of about 2500 ppm. The monitor composition is exposed to the peracetic acid solution under conditions that will cause the monitor composition to undergo a color change at about 2500 ppm of peracetic acid.
The invention also features a method of monitoring a sterilization process that uses a liquid peracid sterilant by contacting a sterilization monitoring device with a liquid peracid from a sterilization solution during the sterilization process. The sterilization monitoring device includes a vapor permeable barrier and a monitor composition. The peracid vapor from the liquid sterilant penetrates the vapor barrier contacting the monitor composition including a colorant susceptible to halogenation and a halogen source, and the peracid contacts the halogen source to produce halogen which halogenates the colorant to cause a color change in the composition.
The invention also features a sterilization monitoring device including a housing having a vapor permeable barrier and a monitor composition enclosed within the housing. The monitor composition includes a halogen source and a colorant susceptible to halogenation in the presence of a peracid from a sterilization solution. The peracid contacts the halogen source to produce halogen which halogenates the colorant to cause a color change in the composition.
The invention also features a sterilization monitoring device including a substrate, having a laminated side, carrying a monitoring composition, and a housing having a vapor permeable barrier. Preferably, the housing also includes a vapor impermeable barrier. The vapor impermeable barrier defines a vapor head space. The substrate is enclosed within the housing with the laminated side mounted to the vapor permeable barrier.
Other features and advantages of the invention will be apparent from the description of the preferred embodiment thereof, and from the claims.